I'm assuming this is in regard to an iPad. Anyway, unless you will be using the device on a cellular network like you do with your smartphone, the Wi-Fi only version should be sufficient, in my opinion.
I woulod always gauge on where am I going to use it and how much am I going to use it where there is no WI-FI available to you. I have WI-FI of course at home and work and when I go out if I take my iPad with me if there is WI-Fi where i am going then I will take it otherwise I don't. I would not have bought an iPad andthis is just me and my own opinion if I had to buy cellular with it. I am lucky that I have Wi-FI almost everywhere so that is what I got. Good luck.
If you are constantly traveling, get the cellular. If you know that you will have wifi access, there is no need to waste money on the cellular version.
My iPad 3 is wifi only because I knew I wasn't going to be carrying it around everywhere but my rMini has cellular because I take it everywhere. If you'll be carrying it all the time, I say go with the cellular to be safe.